The present invention relates to a ceramic having a controlled pore size, and more particularly, to a controlled pore structure, liquid phase sintered ceramics for orthopaedic and dental applications.
Ceramic materials which are useful as bone substitutes are used in numerous orthopaedic and dental applications including as implants. Examples of such bone substitutes are described in U.S. Pat. Nos. 4,097,935 to Jarcho; 4,113,500 to Ebihara et al; 4,149,893 to Aoki et al; and 4,330,514 to Nagai et al.
Two bone substitute materials, hydroxyapatite and tricalcium phosphate, have been approved for general dental implant use, and in some selected instances, orthopaedic clinical trials. However, these materials are only available in particulate or solid bulk closed cell forms. Thus, the use of such materials in orthopaedic and dental applications has been limited.
Bone substitutes such as hydroxyapatite have been combined with other agents in various medical applications. Surgical cements including hydroxyapatite as the bone substitute are used in numerous orthopaedic and dental applications including repairing bone fractures, in attaching bone plates and other prostheses, in bridging comminuted fractures, and in filling or aligning dental cavities. Examples of such compositions are described in U.S. Pat. Nos. 4,518,430 to Brown et al; and 4,542,167 to Aoki et al. U.S. Pat. No. 4,451,235 to Okuda et al discloses a dental root material comprising hydroxyapatite and an organic matrix such as polyethylene.
U.S. Pat. No. 4,135,935 to Pfeil et al discloses a composite material useful as an implant. A first starting material which is preferably an apatite and a second starting material which is preferably a glass are ground, preferably jointly, to a particle size preferably between about 200-500 microns. The resultant mixture is finely comminuted to a particle size preferably between about 20-50 microns. The mixture is compressed to form shaped bodies and sintered. This material does not have the open pore structure which characterizes the ceramic material of the present invention.